Amicus Therapeutics (FOLD) 10-Q 9 May 19 2019 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2019	Apr. 29, 2019
Document And Entity Information [Abstract]
Entity Registrant Name	AMICUS THERAPEUTICS, INC.
Entity Central Index Key	0001178879
Document Type	10-Q
Document Period End Date	Mar. 31, 2019
Amendment Flag	false
Current Fiscal Year End Date	--12-31
Entity Current Reporting Status	Yes
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		230,450,221
Document Fiscal Year Focus	2019
Document Fiscal Period Focus	Q1
Entity emerging growth company	false
Entity small business	false

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Current assets:
Cash and cash equivalents	$ 96,349	$ 79,749
Investments in marketable securities	341,978	424,403
Accounts receivable	22,960	21,962
Inventories	8,167	8,390
Prepaid expenses and other current assets	13,592	16,592
Total current assets	483,046	551,096
Operating and finance lease right-of-use assets, less accumulated amortization of $2,111 and $0 at March 31, 2019 and December 31, 2018, respectively	36,308
Property and equipment, less accumulated depreciation of $15,794 and $15,671 at March 31, 2019 and December 31, 2018, respectively	13,286	11,375
In-process research & development	23,000	23,000
Goodwill	197,797	197,797
Other non-current assets	11,265	6,683
Total Assets	764,702	789,951
Current liabilities:
Accounts payable, accrued expenses, and other current liabilities	60,596	80,625
Deferred reimbursements	2,750	5,500
Operating and finance lease liabilities	2,523
Total current liabilities	65,869	86,125
Deferred reimbursements	11,406	10,156
Convertible notes	22,052	175,006
Senior secured term loan	146,766	146,734
Contingent consideration payable	20,767	19,700
Deferred income taxes	6,465	6,465
Operating and finance lease liabilities	36,100
Other non-current liabilities	3,609	2,853
Total liabilities	313,034	447,039
Commitments and contingencies
Stockholders’ equity:
Common stock, $0.01 par value, 500,000,000 shares authorized, 230,180,714 and 189,383,924 shares issued and outstanding at March 31, 2019 and December 31, 2018, respectively	2,347	1,942
Additional paid-in capital	1,970,607	1,740,061
Accumulated other comprehensive loss:
Foreign currency translation adjustment	(1,309)	495
Unrealized gain on available-for-sale securities	157	(427)
Warrants	12,387	13,063
Accumulated deficit	(1,532,521)	(1,412,222)
Total stockholders’ equity	451,668	342,912
Total Liabilities and Stockholders’ Equity	$ 764,702	$ 789,951

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Statement of Financial Position [Abstract]
Less accumulated depreciation and amortization on finance and operating lease right-of-use leases	$ 2,111
Accumulated depreciation of property and equipment	$ 15,794	$ 15,671
Common stock, par value (in dollars per share)	$ 0.01	$ 0.01
Common stock, shares authorized	500,000,000	500,000,000
Common stock, shares issued	230,180,714	189,383,924
Common stock, shares outstanding	230,180,714	189,383,924

Consolidated Statements of Oper

Consolidated Statements of Operations - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Revenue:
Net product sales	$ 34,046	$ 16,696
Cost of goods sold	4,055	2,615
Gross profit	29,991	14,081
Operating expenses:
Research and development	64,593	40,798
Selling, general and administrative	44,303	27,396
Changes in fair value of contingent consideration payable	1,383	1,100
Depreciation and amortization	991	969
Total operating expenses	111,270	70,263
Loss from operations	(81,279)	(56,182)
Other income (expense):
Interest income	2,639	1,737
Interest expense	(6,454)	(4,488)
Loss on exchange of convertible notes	(36,123)	0
Change in fair value of derivatives	0	4,861
Other (expense) income	1,086	2,764
Loss before income tax	(120,131)	(51,308)
Income tax benefit	(168)	1,392
Net loss attributable to common stockholders	$ (120,299)	$ (49,916)
Net loss attributable to common stockholders per common share - basic and diluted (in dollars per share)	$ (0.56)	$ (0.28)
Weighted-average common shares outstanding - basic and diluted (in shares)	213,519,287	175,977,700

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (120,299)	$ (49,916)
Other comprehensive (loss) gain:
Foreign currency translation adjustment gain (loss), net of tax impact of $0 and $0, respectively	(1,804)	(1,805)
Unrealized gain (loss) on available-for-sale securities	584	(441)
Other comprehensive income (loss)	(1,220)	(2,246)
Comprehensive loss	$ (121,519)	$ (52,162)

Consolidated Statements of Co_2

Consolidated Statements of Comprehensive Loss (Parenthetical) - USD ($)	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Statement of Comprehensive Income [Abstract]
Foreign currency translation adjustment gain (loss), tax (benefit) expense	$ 0	$ 0

Consolidated Statements of Chan

Consolidated Statements of Changes in Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock	Additional Paid-In Capital	Outstanding warrants, convertible to common stock	Other Comprehensive Gain (Loss)	Accumulated Deficit
Balance at Dec. 31, 2017	$ 352,850	$ 1,721	$ 1,400,758	$ 16,076	$ (2,095)	$ (1,063,610)
Balance (in shares) at Dec. 31, 2017		166,989,790
Increase (Decrease) in Stockholders' Equity
Stock issued from exercise of stock options, net	3,978	$ 6	3,972
Stock issued from exercise of stock options, net (in shares)		560,721
Stock issued from equity financing	294,584	$ 202	294,382
Stock issued from equity financing (in shares)		20,239,839
Restricted stock tax vesting	(1,912)		(1,912)
Restricted stock tax vesting (in shares)		181,868
Stock issued for contingent consideration	0	$ 0	0
Stock issued for contingent consideration (in shares)		0
Stock-based compensation	7,478		7,478
Change in fair value of derivatives	(83,199)		(83,199)
Unrealized holding gain on available-for-sale securities	(441)				(441)
Foreign currency translation adjustment	(1,805)				(1,805)
Net loss	(49,916)					(49,916)
Balance at Mar. 31, 2018	521,617	$ 1,929	1,621,479	16,076	(4,724)	(1,113,143)
Balance (in shares) at Mar. 31, 2018		187,972,218
Balance at Dec. 31, 2018	$ 342,912	$ 1,942	1,740,061	13,063	68	(1,412,222)
Balance (in shares) at Dec. 31, 2018	189,383,924	189,383,924
Increase (Decrease) in Stockholders' Equity
Stock issued from exercise of stock options, net	$ 3,953	$ 6	3,947
Stock issued from exercise of stock options, net (in shares)		578,451
Restricted stock tax vesting	(1,940)	$ 0	(1,940)
Restricted stock tax vesting (in shares)		301,058
Stock issued for contingent consideration	9,316	$ 8	9,308
Stock issued for contingent consideration (in shares)		771,804
Stock-based compensation	12,744		12,744
Warrants exercised	812	$ 1	1,487	(676)
Warrants exercised (in shares)		101,787
Equity component of the convertible notes	190,758	$ 390	190,368
Equity component of the convertible notes (in shares)		39,043,690
Termination of capped call confirmations	14,632		14,632
Unrealized holding gain on available-for-sale securities	584				584
Foreign currency translation adjustment	(1,804)				(1,804)
Net loss	(120,299)					(120,299)
Balance at Mar. 31, 2019	$ 451,668	$ 2,347	$ 1,970,607	$ 12,387	$ (1,152)	$ (1,532,521)
Balance (in shares) at Mar. 31, 2019	230,180,714	230,180,714

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Operating activities
Net loss	$ (120,299)	$ (49,916)
Adjustments to reconcile net loss to net cash used in operating activities:
Amortization of debt discount and deferred financing	1,649	2,601
Depreciation and amortization	991	969
Stock-based compensation	12,744	7,478
Loss on exchange of convertible debt	36,123	0
Change in fair value of derivatives	0	(4,861)
Non-cash changes in the fair value of contingent consideration payable	1,383	1,100
Foreign currency remeasurement (gain) loss	325	(2,957)
Changes in operating assets and liabilities:
Accounts receivable	(1,001)	(1,047)
Inventories	345	(3,253)
Prepaid expenses and other current assets	3,059	10,875
Accounts payable and accrued expenses	(8,858)	(10,347)
Other non-current assets and liabilities	(3,507)	(163)
Deferred reimbursements	(1,500)	0
Net cash used in operating activities	(78,546)	(49,521)
Investing activities
Sale and redemption of marketable securities	135,187	121,226
Purchases of marketable securities	(52,178)	(303,010)
Capital expenditures	(2,944)	(819)
Net cash used in investing activities	80,065	(182,603)
Financing activities
Proceeds from issuance of common stock, net of issuance costs	0	294,584
Payment of finance leases	(75)
Payment of finance leases		(71)
Purchase of vested restricted stock units	(1,938)	(1,912)
Proceeds from termination of capped call confirmations	14,632	0
Proceeds from exercise of stock options	3,953	3,978
Proceeds of exercise of warrants	812	0
Net cash provided by financing activities	17,384	296,579
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(2,350)	860
Net decrease in cash, cash equivalents and restricted cash	16,553	65,315
Cash, cash equivalents and restricted cash at beginning of period	82,375	51,237
Cash, cash equivalents and restricted cash at end of period	98,928	116,552
Cash paid during the period for interest
Capital expenditures, unpaid	4,846	12
Capital expenditures, unpaid	0	142
Payment of contingent consideration in shares	$ 9,316	$ 0

Business

Business	3 Months Ended
	Mar. 31, 2019
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Business	Business Amicus Therapeutics, Inc. (the "Company") is a global patient-dedicated biotechnology company engaged in the discovery, development and commercialization of a diverse set of novel treatments for patients living with rare metabolic diseases. With one medicine for Fabry disease that has achieved widespread global approval, a differentiated biologic for Pompe disease in the clinic and the recent addition of fourteen new gene therapy programs into the pipeline, including two clinical stage gene therapies for Batten disease, the Company has a leading portfolio of therapies for lysosomal storage disorders ("LSDs"). The cornerstone of the Company's portfolio is Galafold ® (also referred to as "migalastat"), the first and only approved oral precision medicine for people living with Fabry disease who have amenable genetic variants. Migalastat is currently approved under the trade name Galafold ® in the United States ("U.S."), European Union ("EU") and Japan, with additional approvals granted and applications pending in several other geographies. During the third quarter of 2018, the Company initiated the commercial launch of Galafold ® in the U.S. for the treatment of adult patients with a confirmed diagnosis of Fabry disease and an amenable genetic variant. The lead biologics program of the Company's pipeline is Amicus Therapeutics GAA ("AT-GAA", also known as ATB200/AT2221), a novel, clinical-stage, potential best-in-class treatment paradigm for Pompe disease. In February 2019, the U.S. Food and Drug Administration ("FDA") granted Breakthrough Therapy Designation to AT-GAA for the treatment of late onset Pompe disease. The Company's Chaperone-Advanced Replacement Therapy ("CHART ® ") platform technology is leveraged to develop novel products for Pompe disease and potentially other LSDs in the future. With 14 new gene therapy programs, the Company has established a leading portfolio of medicines for people living with rare metabolic disorders. Through a license with NCH and collaboration with Penn, the Company's pipeline includes gene therapy programs in rare, neurologic LSDs with lead programs in CLN6, CLN3, and CLN8 Batten disease, Pompe disease, Fabry disease, CDKL5 deficiency disorder ("CDD") and one additional undisclosed rare metabolic disorder. The Company believes that its platform technologies and product pipeline uniquely positions it and drives its commitment to advancing and expanding a robust pipeline of cutting-edge, first- or best-in-class medicines for rare metabolic diseases. During the first quarter of 2019, the Company entered into separate, privately negotiated exchange agreements with a limited number of holders (the "Holders") of the Convertible Notes. Under the terms of the exchange agreements, the Holders agreed to exchange an aggregate principal amount of approximately $219.3 million of Convertible Notes held by them in exchange for an aggregate of approximately 39.0 million shares of the our common stock, par value $0.01 per share. The Company had an accumulated deficit of approximately $1.5 billion as of March 31, 2019 and anticipates incurring losses through the fiscal year ending December 31, 2019 and beyond. The Company has been able to fund its operating losses to date through stock offerings, debt issuances, payments from partners during the terms of the collaboration agreements, other financing arrangements. The current cash position, including expected Galafold ® revenues, is sufficient to fund ongoing Fabry, Pompe and gene therapy program operations into at least mid-2021. Potential future business development collaborations, pipeline expansion, and investment in manufacturing capabilities could impact the Company's future capital requirements.

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	Summary of Significant Accounting Policies Basis of Presentation The Company has prepared the accompanying unaudited consolidated financial statements in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") for interim financial information and with the instructions to Form 10-Q and Article 10-01 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by U.S. GAAP for complete financial statements. In the opinion of management, the accompanying unaudited financial statements reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company's interim financial information The accompanying unaudited consolidated financial statements and related notes should be read in conjunction with the Company's financial statements and related notes as contained in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2018 . For a complete description of the Company's accounting policies, please refer to the Annual Report on Form 10-K for the fiscal year ended December 31, 2018 . Consolidation The consolidated financial statements include the accounts of the Company and its subsidiaries. Intercompany accounts and transactions have been eliminated in consolidation. Foreign Currency Transactions The functional currency for most of the Company's foreign subsidiaries is their local currency. For non-U.S. subsidiaries that transact in a functional currency other than the U.S. dollar, assets and liabilities are translated at current rates of exchange at the balance sheet date. Income and expense items are translated at the average foreign exchange rates for the period. Adjustments resulting from the translation of the financial statements of the Company's foreign operations into U.S. dollars are excluded from the determination of net income and are recorded in accumulated other comprehensive income, a separate component of stockholders' equity. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates. Reclassification Certain prior year amounts have been reclassified for comparative purposes. The reclassifications did not affect results of operations, net assets or cash flows. Cash, Cash Equivalents, Marketable Securities and Restricted Cash The Company considers all highly liquid investments purchased with a maturity of three months or less at the date of acquisition, to be cash equivalents. Marketable securities consist of fixed income investments with a maturity of greater than three months and other highly liquid investments that can be readily purchased or sold using established markets. These investments are classified as available-for-sale and are reported at fair value on the Company's consolidated balance sheet. Unrealized holding gains and losses are reported within comprehensive income (loss) in the statements of comprehensive loss. Fair value is based on available market information including quoted market prices, broker or dealer quotations or other observable inputs. Restricted cash consists primarily of funds held to satisfy the requirements of certain agreements that are restricted in their use and is included in non-current assets on the Company's consolidated balance sheet. Concentration of Credit Risk The Company's financial instruments that are exposed to concentration of credit risk consist primarily of cash and cash equivalents and marketable securities. The Company maintains its cash and cash equivalents in bank accounts, which, at times, exceed federally insured limits. The Company invests its marketable securities in high-quality commercial financial instruments. The Company has not recognized any losses from credit risks on such accounts during any of the periods presented. The Company believes it is not exposed to significant credit risk on cash and cash equivalents or its marketable securities. The Company is subject to credit risk from its accounts receivable related to its product sales of Galafold ® . The Company's accounts receivable at March 31, 2019 have arisen from product sales primarily in the EU and U.S. The Company will periodically assess the financial strength of its customers to establish allowances for anticipated losses, if any. For accounts receivable that have arisen from named patient sales, the payment terms are predetermined and the Company evaluates the creditworthiness of each customer on a regular basis. During the three months ended March 31, 2019 , the Company recorded an allowance for doubtful accounts of $0.3 million . Revenue Recognition The Company's net product sales consist of sales of Galafold ® for the treatment of Fabry disease. The Company has recorded revenue on sales where Galafold ® is available either on a commercial basis or through a reimbursed early access program ("EAP"). Orders for Galafold ® are generally received from distributors and pharmacies with the ultimate payor often a government authority. The Company recognizes revenue when its performance obligations to its customers have been satisfied, which occurs at a point in time when the pharmacies or distributors obtain control of Galafold ® . The transaction price is determined based on fixed consideration in the Company's customer contracts and is recorded net of estimates for variable consideration, which are third party discounts and rebates. The identified variable consideration is recorded as a reduction of revenue at the time revenues from sales of Galafold ® are recognized. The Company recognizes revenue to the extent that it is probable that a significant revenue reversal will not occur in a future period. These estimates may differ from actual consideration received. The Company evaluates these estimates each reporting period to reflect known changes. The following table summarizes the Company's net product sales from Galafold ® disaggregated by geographic area: Three Months Ended March 31, (in thousands) 2019 2018 U.S. $ 9,068 $ — Ex-U.S. 24,978 16,696 Total net product sales $ 34,046 $ 16,696 Inventories and Cost of Goods Sold Inventories are stated at the lower of cost and net realizable value, determined by the first-in, first-out method. Inventories are reviewed periodically to identify slow-moving or obsolete inventory based on projected sales activity as well as product shelf-life. In evaluating the recoverability of inventories produced, the probability that revenue will be obtained from the future sale of the related inventory is considered and inventory value is written down for inventory quantities in excess of expected requirements. Expired inventory is disposed of and the related costs are recognized as cost of goods sold in the consolidated statements of operations. Cost of goods sold includes the cost of inventory sold, manufacturing and supply chain costs, product shipping and handling costs, provisions for excess and obsolete inventory, as well as royalties payable. A portion of the inventory available for sale was expensed as research and development costs prior to regulatory approval and as such the cost of goods sold and related gross margins are not necessarily indicative of future cost of goods sold and gross margin. Leases In the ordinary course of business, the Company enters into lease agreements for office space as well as leases for certain property and equipment. The leases have varying terms and expirations and have provisions to extend or renew the lease agreement, among other terms and conditions, as negotiated. The Company determines if an arrangement is a lease at inception. Operating and finance leases are included in right-of-use ("ROU") assets and lease liabilities on the Company's consolidated balance sheets. ROU assets represent the Company's right to control the use of an explicitly or implicitly identified fixed asset for a period of time and lease liabilities represent the Company's obligation to make lease payments arising from the lease. Control of an underlying asset is conveyed to the Company if the Company obtains the rights to direct the use of and to obtain substantially all of the economic benefits from using the underlying asset. ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. Lease payments included in the measurement of the lease liability are comprised of fixed payments. Variable lease payments are excluded from the ROU assets and lease liabilities and are recognized in the period in which the obligation for those payments are incurred. Variable lease payments are presented in the Company's consolidated statements of operations in the same line item as expense arising from fixed lease payments for operating leases. The Company has lease agreements which include lease and non-lease components, which the Company accounts for as a single lease component for all underlying asset categories. A lessee is required to discount its unpaid lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. As most of the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The lease term for all the Company's leases includes the non-cancellable period of the lease plus any additional periods covered by either a Company option to extend (or not to terminate) the lease that the Company is reasonably certain to exercise, or an option to extend (or not to terminate) the lease controlled by the lessor. Leases with an initial term of 12 months or less are not recorded on the balance sheet. The Company recognizes lease expense for these leases on a straight-line basis over the lease term. The Company applies this policy to all underlying asset categories. The information presented for the periods prior to January 1, 2019 has not been restated and is reported under the accounting standard in effect for those periods. For additional information, see " —Note 9. Leases" and "—Note 2. Summary of Significant Accounting Policies, Recent Accounting Developments - Guidance Adopted in 2019." Recent Accounting Developments - Guidance Adopted in 2019 ASU 2016-02 - In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) ("ASU 2016-02"). ASU 2016-02 requires the recognition of lease assets and lease liabilities on the balance sheet for all lease obligations and disclosing key information about leasing arrangements. ASU 2016-02 requires the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous generally accepted accounting principles. ASU 2016-02 will be effective for the Company for all annual and interim periods beginning after December 15, 2018, including interim periods within those fiscal years. In August 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements , ("ASU 2018-11"). ASU 2018-11 provide entities with an additional transition method for adoption, whereby, an entity initially applies the new leases standard at the adoption date and recognizes a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. Effective January 1, 2019 the Company adopted ASU 2016-02, along with the amendments issued in 2017 and 2018, and elected the transition method in ASU 2018-11. The Company elected the package of transition provisions available for expired or existing contracts, which allowed the Company to carry forward its historical assessments of (i) whether contracts are or contain leases, (ii) lease classification and (iii) initial direct costs. In addition, the Company applied the short-term lease recognition exemption for leases with terms at inception not greater than 12 months and will apply the practical expedient not to separate lease and non-lease components for new and modified leases commencing after adoption. The information presented for the periods prior to January 1, 2019 has not been restated and is reported under the accounting standard in effect for those periods. Upon adoption, the Company recorded a lease liabilities with a corresponding right-of-use assets of $17.6 million . The adoption did not have a material impact on the consolidated results of operations and cash flows for the three-months ended March 31, 2019. In August 2018, the Securities Exchange Commission ("SEC") issued Final Rule 33-10532, Disclosure Update and Simplification , which amends certain disclosure requirements that were redundant, duplicative, overlapping or superseded by other SEC disclosure requirements. The amendments generally eliminated or otherwise reduced certain disclosure requirements of various SEC rules and regulations. However, in some cases, the amendments require additional information to be disclosed, including changes in stockholders' equity in interim periods. The rule is effective 30 days after its publication in the Federal Register. The rule was posted on October 4, 2018. On September 25, 2018, the SEC released guidance advising it will not object to a registrant adopting the requirement to include changes in stockholders' equity in the Form 10-Q for the first quarter beginning after the effective date of the rule. The Company adopted the guidance in this Form 10-Q for the period ended March 31, 2019. Recent Accounting Developments - Guidance Not Yet Adopted ASU 2018-13 — In August 2018, the FASB issued ASU 2018-03, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement ("ASU 2018-13"). The amendments modify the disclosure requirements in Topic 820. ASU 2018-13 is effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. Early adoption is permitted. An entity is permitted to early adopt any removed or modified disclosures upon issuance of ASU 2018-13 and delay adoption of the additional disclosures until their effective date. The Company is currently assessing the impact that this standard will have on its consolidated financial statements upon adoption. ASU 2017-08 — In March 2017, the FASB issued ASU 2017-08, Receivables—Nonrefundable Fees and Other Costs (Subtopic 310-20), Premium Amortization on Purchased Callable Debt Securities ("ASU 2017-08") . The amendments in ASU 2017-08 shorten the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. ASU 2017-08 is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted, including adoption in an interim period. If an entity early adopts in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. The amendments should be applied on a modified retrospective basis, with a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. ASU 2017-04 — In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment ("ASU 2017-04"). To simplify the subsequent measurement of goodwill, ASU 2017-04 eliminates Step 2 from the goodwill impairment test. The annual, or interim, goodwill impairment test is performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge should be recognized for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. In addition, income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit should be considered when measuring the goodwill impairment loss, if applicable. ASU 2017-04 also eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment and, if it fails that qualitative test, to perform Step 2 of the goodwill impairment test. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. ASU 2017-04 should be applied on a prospective basis. The nature of and reason for the change in accounting principle should be disclosed upon transition. A public business entity that is a U.S. SEC filer should adopt ASU 2017-04 for its annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. ASU 2016-13 — I n June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). ASU 2016-13 requires financial assets measured at amortized cost basis to be presented at the net amount expected to be collected and amends guidance on the impairment of financial instruments. ASU 2016-13 is effective for public companies who are SEC filers for fiscal years beginning after December 15, 2019, including interim periods within those years. The Company expects to adopt this guidance when effective and is currently assessing the impact that this standard will have on its consolidated financial statements.

Cash, Cash Equivalents, Marketa

Cash, Cash Equivalents, Marketable Securities and Restricted Cash	3 Months Ended
	Mar. 31, 2019
Cash, Cash Equivalents, and Short-term Investments [Abstract]
Cash, Cash Equivalents, Marketable Securities and Restricted Cash	Cash, Cash Equivalents, Marketable Securities and Restricted Cash As of March 31, 2019 , the Company held $96.3 million in cash and cash equivalents and $342.0 million of available-for-sale debt securities which are reported at fair value on the Company's consolidated balance sheets. Unrealized holding gains and losses are reported within accumulated other comprehensive loss in the statements of comprehensive loss. If a decline in the fair value of a marketable security below the Company's cost basis is determined to be other-than-temporary, such marketable security is written down to its estimated fair value as a new cost basis and the amount of the write-down is included in earnings as an impairment charge. The Company regularly invests excess operating cash in deposits with major financial institutions, money market funds, notes issued by the U.S. government, as well as fixed income investments and U.S. bond funds, both of which can be readily purchased and sold using established markets. The Company believes that the market risk arising from its holdings of these financial instruments is mitigated as many of these securities are either government backed or of the highest credit rating. Investments that have original maturities greater than three months but less than one year are classified as current, while investments that have maturities greater than one year are classified as long-term. Cash, cash equivalents and marketable securities are classified as current unless mentioned otherwise below and consisted of the following: As of March 31, 2019 (in thousands) Cost Gross unrealized Gain Gross unrealized Loss Fair Value Cash and cash equivalents $ 96,349 $ — $ — $ 96,349 Corporate debt securities, current portion 138,194 96 (6 ) 138,284 Commercial paper 134,948 52 (7 ) 134,993 Asset-backed securities 68,278 30 (8 ) 68,300 Money market 350 — — 350 Certificates of deposit 51 — — 51 $ 438,170 $ 178 $ (21 ) $ 438,327 Included in cash and cash equivalents $ 96,349 $ — $ — $ 96,349 Included in marketable securities, current and non-current 341,821 178 (21 ) 341,978 Total cash, cash equivalents and marketable securities $ 438,170 $ 178 $ (21 ) $ 438,327 As of December 31, 2018 (in thousands) Cost Gross unrealized Gain Gross unrealized Loss Fair Value Cash and cash equivalents $ 79,749 $ — $ — $ 79,749 Corporate debt securities, current portion 240,969 7 (250 ) 240,726 Commercial paper 115,245 — (104 ) 115,141 Asset-backed securities 68,215 4 (84 ) 68,135 Money market 350 — — 350 Certificates of deposit 51 — — 51 $ 504,579 $ 11 $ (438 ) $ 504,152 Included in cash and cash equivalents $ 79,749 $ — $ — $ 79,749 Included in marketable securities 424,830 11 (438 ) 424,403 Total cash, cash equivalents and marketable securities $ 504,579 $ 11 $ (438 ) $ 504,152 For the three months ended March 31, 2019 there were no realized gains. For the fiscal year ended December 31, 2018 , there were no minal realized gains. The cost of securities sold is based on the specific identification method. Unrealized loss positions in the available-for-sale debt securities as of March 31, 2019 and December 31, 2018 reflect temporary impairments that have been in a loss position for less than twelve months and as such are recognized in other comprehensive gain (loss). The fair value of these available-for-sale debt securities in unrealized loss positions was $100.4 million and $403.1 million as of March 31, 2019 and December 31, 2018 , respectively. The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the Company's consolidated statements of cash flows. (in thousands) March 31, 2019 December 31, 2018 March 31, 2018 December 31, 2017 Cash and cash equivalents $ 96,349 $ 79,749 $ 114,322 $ 49,060 Restricted cash 2,579 2,626 2,230 2,177 Cash and cash equivalents and restricted cash shown in the statement of cash flows $ 98,928 $ 82,375 $ 116,552 $ 51,237

Inventories

Inventories	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
Inventories	Inventories Inventories consist of raw materials, work-in-process and finished goods related to the manufacture of Galafold ® . The following table summarizes the components of inventories: (in thousands) March 31, 2019 December 31, 2018 Raw materials $ 1,321 $ 1,291 Work-in-process $ 3,041 3,485 Finished goods 3,805 3,614 Total inventories $ 8,167 $ 8,390 The Company recorded a reserve for inventory of $0.2 million as of March 31, 2019 and December 31, 2018.

Debt

Debt	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Debt	Debt Senior Secured Term Loan due 2023 In September 2018, the Company entered into a loan agreement with BioPharma Credit PLC as the lender. The loan agreement provides for a $150 million senior secured term loan ("Senior Secured Term Loan") with an interest rate equal to the 3-month LIBOR plus 7.50% per annum and matures 5 years from the maturity date. The Senior Secured Term Loan will be repaid in four quarterly payments equal to 12.50% thereof starting on the forty-eight month anniversary of the date of the first credit extension with the balance due on the Maturity Date. Interest is payable quarterly in arrears. The Senior Secured Term Loan contains certain customary representations and warranties, affirmative and negative covenants and events of default applicable to the Company and certain of its subsidiaries, but does not include any financial covenants relating to the achievement or maintenance of revenue or cash flow. If an event of default occurs and is continuing, the lender may declare all amounts outstanding under the Senior Secured Term Loan to be immediately due and payable. The Company received net proceeds of $146.6 million in September 2018, after deducting fees and estimated expenses payable by the Company . Convertible Notes due 2023 In December 2016, the Company issued at par value $250 million aggregate principal amount of unsecured Convertible Senior Notes due 2023 (the "Convertible Notes"), which included the exercise in full of the $25 million over-allotment option granted to the initial purchasers of the Convertible Notes in a private offering to qualified institutional buyers pursuant to Rule 144A under the Securities Act (the "Note Offering"). Interest is payable semiannually on June 15 and December 15 of each year, beginning on June 15, 2017. The Convertible Notes will mature on December 15, 2023, unless earlier repurchased, redeemed, or converted in accordance with their terms. The Convertible Notes are convertible at the option of the holders, under certain circumstances and during certain periods, into cash, shares of the Company's common stock or a combination thereof. The net proceeds from the Note Offering were $243.0 million , after deducting fees and estimated expenses payable by the Company. In addition, the Company used approximately $13.5 million of the net proceeds from the issuance of the Convertible Notes to pay the cost of the capped call transactions ("Capped Call Confirmations") that the Company entered into in connection with the issuance of the Convertible Notes. In accounting for the issuance of the Convertible Notes, the Company separated the Convertible Notes into liability and equity components based on their relative values. The Convertible Notes are initially convertible into approximately 40,849,675 shares of the Company's common stock under certain circumstances prior to maturity at a conversion rate of 163.3987 shares per $1,000 principal amount of Convertible Notes, which represents a conversion price of approximately $6.12 per share of the Company's common stock, subject to adjustment under certain conditions. The last reported sale price of the Company's common stock was equal to or more than 130% of the conversion price of the Convertible Notes for at least 20 trading days of the 30 consecutive trading days ending on the last day of the second quarter. As a result, the Convertible Notes are currently convertible into the Company's common stock. On February 15, 2018, the Company entered into an underwriting agreement relating to an underwritten public offering of 19,354,839 shares of the Company's common stock. Under the terms of the underwriting agreement, the Company granted the underwriters an option, exercisable for 30 days after February 16, 2018, to purchase up to an additional 2,903,225 shares of the Company's common stock, which was exercised with respect to 885,000 shares of the Company's common stock. Subsequent to the underwritten public offering on February 15, 2018, the Company did not have sufficient unissued authorized shares to cover a conversion of the Convertible Notes. As a result, the Company accounted for the portion of the bifurcated conversion feature and of the Capped Call Confirmations that would not be able to be net share settled as a current derivative liability and as a derivative asset, respectively. The fair value of the derivative liability for the conversion feature and derivative asset for the Capped Call Confirmations at February 15, 2018 was determined to be $507.4 million and $13.6 million , respectively, of which the portion that was determined to not be able to be net share settled was recorded with a corresponding impact to additional-paid-in-capital. Subsequent changes to fair value of the derivatives were recorded through earnings on the Company's consolidated statements of operations resulting in a change in fair value of derivatives for the three months ended March 31, 2018 of $4.9 million . As of March 31, 2018, the Company recorded the fair value of the derivative liability of $80.6 million as a current liability and the fair value of the Capped Call Confirmation of $2.2 million as a current asset within Other Current Assets on the consolidated balance sheets. During the first quarter of 2019, the Company entered into separate, privately negotiated exchange agreements with a limited number of holders (the "Holders") of the Convertible Notes. Under the terms of the exchange agreements (the "Exchange Agreements"), the Holders agreed to exchange an aggregate principal amount of approximately $219.3 million of Convertible Notes held by them in exchange for an aggregate of approximately 39.0 million shares of the our common stock, par value $0.01 per share. In addition, pursuant to the Exchange Agreements, the Company made aggregate cash payments of approximately $1.0 million to the Holders to satisfy accrued and unpaid interest to the closing date of the transaction, along with cash in lieu of fractional shares. As a result of this exchange, the Company recognized a loss on exchange of debt of $36.1 million in the consolidated statement of operations, and $190.4 million in additional paid-in-capital and common stock of $ 0.4 million in the consolidated balance sheets for the three months ended March 31, 2019. During the first quarter of 2019, the Company also terminated the proportion of the Capped Call Confirmations related to the exchange of the Convertible Notes during the first quarter of 2019 for proceeds of approximately $14.6 million . The Convertible Notes and Senior Secured Term Loan consist of the following: Liability component (in thousands) March 31, 2019 December 31, 2018 Principal 180,702 $ 400,000 Less: debt discount (1) (11,076 ) (74,145 ) Less: deferred financing (1) (808 ) (4,115 ) Net carrying value of the debt $ 168,818 $ 321,740 ______________________________________ (1) Included in the consolidated balance sheets within Convertible Notes and Senior Secured Term Loan and amortized to interest expense over the remaining life of the Convertible Notes and Senior Secured Term Loan using the effective interest rate method. The following table sets forth total interest expense recognized related to the Convertible Notes and Senior Secured Term Loan for the three months ended March 31, 2019 and 2018, respectively: Three Months Ended March 31, Interest component (in thousands) 2019 2018 Contractual interest expense 4,813 $ 1,887 Amortization of debt discount 1,559 2,472 Amortization of deferred financing 83 129 Total $ 6,455 $ 4,488

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2019
Equity [Abstract]
Stockholders' Equity	Stockholders' Equity During the three months ended March 31, 2019, 101,787 warrants were exercised at $7.98 per share of common stock resulting in gross cash proceeds of $0.8 million . As discussed in ''— Note 5. Debt'' during the first quarter of 2019, the Company entered into separate, privately negotiated exchange agreements with a limited number of holders (the "Holders") of the Convertible Notes. Under the terms of the exchange agreements (the "Exchange Agreements"), the Holders agreed to exchange an aggregate principal amount of approximately $219.3 million of Convertible Notes held by them in exchange for an aggregate of approximately 39.0 million shares of the our common stock, par value $0.01 per share. As further discussed in "— Note 8. Assets and Liabilities Measured at Fair Value," the Company reached a clinical milestone, which was the dosing of the first patient in a Phase 3 study, related to the contingent consideration from the acquisition of Callidus. The milestone for this event was $9.0 million which was paid in Company stock during the three months ended March 31, 2019, resulting in $9.3 million impact on stockholder's equity.

Share based Compensation

Share based Compensation	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Share based Compensation	Share based Compensation The Company's Equity Incentive Plans consist of the Amended and Restated 2007 Equity Incentive Plan (the "Plan") and the 2007 Director Option Plan (the "2007 Director Plan"). The Plan provides for the granting of restricted stock units and options to purchase common stock in the Company to employees, directors, advisors and consultants at a price to be determined by the Company's Board of Directors. The Plan is intended to encourage ownership of stock by employees and consultants of the Company and to provide additional incentives for them to promote the success of the Company's business. The 2007 Director Plan is intended to promote the recruiting and retention of highly qualified eligible directors and strengthen the commonality of interest between directors and stockholders by encouraging ownership of common stock of the Company. The Board of Directors, or its committee, is responsible for determining the individuals to be granted options, the number of options each individual will receive, the option price per share, and the exercise period of each option. Stock Option Grants The fair value of the stock options granted is estimated on the date of grant using a Black-Scholes option pricing model with the following weighted-average assumptions: Three Months Ended March 31, 2019 2018 Expected stock price volatility 74.2 % 81.2 % Risk free interest rate 2.5 % 2.3 % Expected life of options (years) 5.68 5.67 Expected annual dividend per share $ — $ — The average expected life is determined using our actual historical data. A summary of the Company's stock options for the three months ended March 31, 2019 were as follows: Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Life Aggregate Intrinsic Value (in thousands) (in millions) Options outstanding, December 31, 2018 15,810 $ 8.63 Granted 3,315 $ 10.15 Exercised (578 ) $ 6.83 Forfeited (195 ) $ 10.33 Expired (21 ) $ 10.77 Options outstanding, March 31, 2019 18,331 $ 8.94 6.9 years $ 90.2 Vested and unvested expected to vest, March 31, 2019 17,325 $ 8.84 6.8 years $ 87.1 Exercisable at March 31, 2019 10,538 $ 7.84 5.5 years $ 62.8 As of March 31, 2019 , the total unrecognized compensation cost related to non-vested stock options granted was $44.1 million and is expected to be recognized over a weighted average period of three years. Restricted Stock Units and Performance-Based Restricted Stock Units (collectively "RSUs") RSUs awarded under the Plan are generally subject to graded vesting and are contingent on an employee's continued service. RSUs are generally subject to forfeiture if employment terminates prior to the release of vesting restrictions. The Company expenses the cost of the RSUs, which is determined to be the fair market value of the shares of common stock underlying the RSUs at the date of grant, ratably over the period during which the vesting restrictions lapse. A summary of non-vested RSU activity under the Plan for the three months ended March 31, 2019 is as follows: Number of Shares Weighted Average Grant Date Fair Value Weighted Average Remaining Years Aggregate Intrinsic Value (in thousands) (in millions) Non-vested units as of December 31, 2018 3,712 $ 10.59 Granted 3,031 $ 10.91 Vested (600 ) $ 9.07 Forfeited (133 ) $ 12.73 Non-vested units as of March 31, 2019 6,010 $ 10.86 3.0 years $ 81.7 For the three months ended March 31, 2019 , 599,734 RSUs have vested and all non-vested units are expected to vest over their normal term. As of March 31, 2019 , there was $48.2 million of total unrecognized compensation cost related to unvested RSUs with service-based vesting conditions. These costs are expected to be recognized over a weighted average period of three years. Compensation Expense Related to Equity Awards The following table summarizes information related to compensation expense recognized in the statements of operations related to the equity awards: Three Months Ended March 31, (in thousands) 2019 2018 Equity compensation expense recognized in: Research and development expense $ 5,032 $ 3,057 Selling, general and administrative expense 7,712 4,421 Total equity compensation expense $ 12,744 $ 7,478

Assets and Liabilities Measured

Assets and Liabilities Measured at Fair Value	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Assets and Liabilities Measured at Fair Value	Assets and Liabilities Measured at Fair Value The Company's financial assets and liabilities are measured at fair value and classified within the fair value hierarchy, which is defined as follows: Level 1 — Quoted prices in active markets for identical assets or liabilities that the Company has the ability to access at the measurement date. Level 2 — Inputs other than quoted prices in active markets that are observable for the asset or liability, either directly or indirectly. Level 3 — Inputs that are unobservable for the asset or liability. A summary of the fair value of the Company's recurring assets and liabilities aggregated by the level in the fair value hierarchy within which those measurements fall as of March 31, 2019 are identified in the following table: (in thousands) Level 2 Total Assets: Commercial paper $ 134,993 $ 134,993 Asset-backed securities 68,300 68,300 Corporate debt securities 138,284 138,284 Money market funds 3,963 3,963 $ 345,540 $ 345,540 Level 2 Level 3 Total Liabilities: Contingent consideration payable $ — $ 20,767 $ 20,767 Deferred compensation plan liability 3,613 — 3,613 $ 3,613 $ 20,767 $ 24,380 A summary of the fair value of the Company's recurring assets and liabilities aggregated by the level in the fair value hierarchy within which those measurements fall as of December 31, 2018 are identified in the following table: (in thousands) Level 2 Total Assets: Commercial paper $ 115,141 $ 115,141 Asset-backed securities 68,135 68,135 Corporate debt securities 240,726 240,726 Money market funds 3,082 3,082 $ 427,084 $ 427,084 Level 2 Level 3 Total Liabilities: Contingent consideration payable $ — $ 19,700 $ 19,700 Deferred compensation plan liability 2,732 — 2,732 $ 2,732 $ 19,700 $ 22,432 The Company's Convertible Notes fall into the Level 2 category within the fair value level hierarchy. The fair value was determined using broker quotes in a non-active market for valuation. The fair value of the debt at March 31, 2019 was approximately $71.6 million . The Company's Senior Secured Term Loan fall into the Level 2 category within the fair value level hierarchy and the fair value was determined using quoted prices for similar liabilities in active markets, as well as inputs that are observable for the liability (other than quoted prices), such as interest rates that are observable at commonly quoted intervals. The carrying value of the Senior Secured Term Loan approximates the fair value. The Company did not have any Level 3 assets as of March 31, 2019 or December 31, 2018 . Cash, Money Market Funds and Marketable Securities The Company classifies its cash within the fair value hierarchy as Level 1 as these assets are valued using quoted prices in an active market for identical assets at the measurement date. The Company considers its investments in marketable securities as available for sale debt securities and classifies these assets and the money market funds within the fair value hierarchy as Level 2 primarily utilizing broker quotes in a non-active market for valuation of these securities. No changes in valuation techniques or inputs occurred during the three months ended March 31, 2019 . No transfers of assets between Level 1 and Level 2 of the fair value measurement hierarchy occurred during the three months ended March 31, 2019 . Contingent Consideration Payable The contingent consideration payable resulted from the acquisition of Callidus Biopharma, Inc. ("Callidus") in November 2013. The most recent valuation was determined using a probability weighted discounted cash flow valuation approach. Using this approach, expected future cash flows are calculated over the expected life of the agreement, are discounted, and then exercise scenario probabilities are applied. The valuation is performed quarterly. Gains and losses are included in the statement of operations. The contingent consideration payable for Callidus has been classified as a Level 3 recurring liability as its valuation requires substantial judgment and estimation of factors that are not currently observable in the market. If different assumptions were used for the various inputs to the valuation approach, the estimated fair value could be significantly higher or lower than the fair value the Company determined. The Company may be required to record losses in future periods. The following significant unobservable inputs were used in the valuation of the contingent consideration payable of Callidus for the ATB200 Pompe program: Contingent Consideration Liability Fair Value as of Valuation Technique Unobservable Input Range (in thousands) Discount rate 10.3% Clinical and regulatory milestones $ 20,538 Probability weighted discounted cash flow Probability of achievement of milestones 75%-78% Projected year of payments 2021-2022 Contingent consideration liabilities are remeasured to fair value each reporting period using discount rates, probabilities of payment and projected payment dates. Projected contingent payment amounts related to clinical and regulatory based milestones are discounted back to the current period using a discounted cash flow model. Increases in discount rates and the time to payment may result in lower fair value measurements. Increases or decreases in any of those inputs together, or in isolation, may result in a significantly lower or higher fair value measurement. There is no assurance that any of the conditions for the milestone payments will be met. The Company reached a clinical milestone, which was the dosing of the first patient in a Phase 3 study, related to the contingent consideration from the acquisition of Callidus. The milestone for this event was $9.0 million which was paid in Company stock during the three months ended March 31, 2019, resulting in $9.3 million impact on stockholder's equity. The following table shows the change in the balance of contingent consideration payable for the three months ended March 31, 2019 and 2018 , respectively: Three Months Ended March 31, (in thousands) 2019 2018 Balance, beginning of the period $ 28,700 $ 25,400 Payment of contingent consideration in stock (9,316 ) — Changes in fair value during the period, included in Statement of Operations 1,383 1,100 Balance, end of the period $ 20,767 $ 26,500 Deferred Compensation Plan - Investment and Liability The Deferred Compensation Plan (the "Deferral Plan") provides certain key employees and members of the Board of Directors with an opportunity to defer the receipt of such participant's base salary, bonus and director's fees, as applicable. Deferral Plan assets are classified as trading securities and recorded at fair value with changes in the investment's fair value recognized in the period they occur. The asset investments consist of market exchanged mutual funds. The Company considers its investments in marketable securities as available-for-sale and classifies these assets and related liability within the fair value hierarchy as Level 2, primarily utilizing broker quotes in a non-active market for valuation of these securities. Derivative asset and liability As of March 31, 2018, as further discussed in "— Note 5. Debt," the Company did not have sufficient unissued authorized shares to cover a conversion of the Convertible Notes. As a result, the Company accounted for the portion of the bifurcated conversion feature and the Capped Call Confirmations that would not be able to be net share settled as a current derivative liability and as a current derivative asset, respectively. The fair value of the debt portion was determined using the discounted cash flow method of the income approach and the fair value of the Capped Call Confirmations was determined using the Black-Scholes model. The derivative asset and liability have been classified as Level 3 recurring as their valuation requires substantial judgment and estimation of factors that are not currently observable in the market. If different assumptions were used for the various inputs to the valuation approach, the estimated fair value could be significantly higher or lower that the fair value determined by the Company.

Leases

Leases	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Leases	Leases The Company currently has operating and finance leases for office and research laboratory space, equipment and vehicles under agreements expiring at various dates through 2044. Certain of the Company's leases contain renewal options to extend the lease for up to 25 years. For the three months ended March 31, 2019, lease expense was $2.1 million and $0.1 million for operating and finance leases, respectively. Cash paid for amounts included in the measurement of operating lease liabilities was $1.4 million for the three months ended March 31, 2019. For the three months ended March 31, 2019, the Company recorded $19.5 million of right-of-use assets obtained in exchange for new operating lease liabilities. Commitments under finance leases are not significant. Supplemental balance sheet information related to operating leases was as follows. (in thousands, except year and discount rate amounts) March 31, 2019 Operating lease ROU asset $ 36,208 Current portion of the operating lease liabilities $ 2,421 Non-current portion of the operating lease liabilities 35,991 Total operating lease liability $ 38,412 Weighted-average remaining lease terms (years) 14.6 Weighted-average discount rate 12.8 % At March 31, 2019 , the future minimum lease payments were as follows: ( in thousands) Operating Leases 2019 (excludes the three months ended March 31, 2019) $ 4,494 2020 9,776 2021 10,516 2022 10,418 2023 10,830 Thereafter 174,006 Total lease payments $ 220,040 Less lease incentives (28,939 ) Less imputed interest (152,689 ) Total operating lease liability $ 38,412 At December 31, 2018 , the future minimum lease payments were as follows: ( in thousands) Operating Leases 2019 $ 6,244 2020 4,063 2021 3,560 2022 3,371 2023 3,611 Thereafter 10,038 Total lease payments $ 30,887
Leases	Leases The Company currently has operating and finance leases for office and research laboratory space, equipment and vehicles under agreements expiring at various dates through 2044. Certain of the Company's leases contain renewal options to extend the lease for up to 25 years. For the three months ended March 31, 2019, lease expense was $2.1 million and $0.1 million for operating and finance leases, respectively. Cash paid for amounts included in the measurement of operating lease liabilities was $1.4 million for the three months ended March 31, 2019. For the three months ended March 31, 2019, the Company recorded $19.5 million of right-of-use assets obtained in exchange for new operating lease liabilities. Commitments under finance leases are not significant. Supplemental balance sheet information related to operating leases was as follows. (in thousands, except year and discount rate amounts) March 31, 2019 Operating lease ROU asset $ 36,208 Current portion of the operating lease liabilities $ 2,421 Non-current portion of the operating lease liabilities 35,991 Total operating lease liability $ 38,412 Weighted-average remaining lease terms (years) 14.6 Weighted-average discount rate 12.8 % At March 31, 2019 , the future minimum lease payments were as follows: ( in thousands) Operating Leases 2019 (excludes the three months ended March 31, 2019) $ 4,494 2020 9,776 2021 10,516 2022 10,418 2023 10,830 Thereafter 174,006 Total lease payments $ 220,040 Less lease incentives (28,939 ) Less imputed interest (152,689 ) Total operating lease liability $ 38,412 At December 31, 2018 , the future minimum lease payments were as follows: ( in thousands) Operating Leases 2019 $ 6,244 2020 4,063 2021 3,560 2022 3,371 2023 3,611 Thereafter 10,038 Total lease payments $ 30,887

Basic and Diluted Net Loss per

Basic and Diluted Net Loss per Common Share	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Basic and Diluted Net Loss per Common Share	Basic and Diluted Net Loss per Common Share The following table provides a reconciliation of the numerator and denominator used in computing basic and diluted net loss attributable to common stockholders per common share: Three Months Ended March 31, (in thousands, except per share amounts) 2019 2018 Numerator: Net loss attributable to common stockholders $ (120,299 ) $ (49,916 ) Denominator: Weighted average common shares outstanding — basic and diluted 213,519,287 175,977,700 Dilutive common stock equivalents would include the dilutive effect of common stock options, convertible debt units, RSUs and warrants for common stock equivalents. Potentially dilutive common stock equivalents were excluded from the diluted earnings per share denominator for all periods because of their anti-dilutive effect. The table below presents potential shares of common stock that were excluded from the computation as they were anti-dilutive using the treasury stock method: As of March 31, (in thousands) 2019 2018 Options to purchase common stock 18,331 16,176 Convertible notes 5,017 40,850 Outstanding warrants, convertible to common stock 2,554 3,110 Unvested restricted stock units 6,010 3,541 Vested restricted stock units, unissued 189 90 Total number of potentially issuable shares 32,101 63,767

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The Company has prepared the accompanying unaudited consolidated financial statements in accordance with accounting principles generally accepted in the United States of America ("U.S. GAAP") for interim financial information and with the instructions to Form 10-Q and Article 10-01 of Regulation S-X. Accordingly, they do not include all of the information and disclosures required by U.S. GAAP for complete financial statements. In the opinion of management, the accompanying unaudited financial statements reflect all adjustments, which include only normal recurring adjustments, necessary to present fairly the Company's interim financial information The accompanying unaudited consolidated financial statements and related notes should be read in conjunction with the Company's financial statements and related notes as contained in the Company's Annual Report on Form 10-K for the fiscal year ended December 31, 2018 . For a complete description of the Company's accounting policies, please refer to the Annual Report on Form 10-K for the fiscal year ended December 31, 2018 .
Consolidation	Consolidation The consolidated financial statements include the accounts of the Company and its subsidiaries. Intercompany accounts and transactions have been eliminated in consolidation.
Foreign Currency Transactions	Foreign Currency Transactions The functional currency for most of the Company's foreign subsidiaries is their local currency. For non-U.S. subsidiaries that transact in a functional currency other than the U.S. dollar, assets and liabilities are translated at current rates of exchange at the balance sheet date. Income and expense items are translated at the average foreign exchange rates for the period. Adjustments resulting from the translation of the financial statements of the Company's foreign operations into U.S. dollars are excluded from the determination of net income and are recorded in accumulated other comprehensive income, a separate component of stockholders' equity.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenues and expenses during the reporting periods. Actual results could differ from those estimates.
Reclassification	Reclassification Certain prior year amounts have been reclassified for comparative purposes. The reclassifications did not affect results of operations, net assets or cash flows.
Cash, Cash Equivalents, Marketable Securities and Restricted Cash	Cash, Cash Equivalents, Marketable Securities and Restricted Cash The Company considers all highly liquid investments purchased with a maturity of three months or less at the date of acquisition, to be cash equivalents. Marketable securities consist of fixed income investments with a maturity of greater than three months and other highly liquid investments that can be readily purchased or sold using established markets. These investments are classified as available-for-sale and are reported at fair value on the Company's consolidated balance sheet. Unrealized holding gains and losses are reported within comprehensive income (loss) in the statements of comprehensive loss. Fair value is based on available market information including quoted market prices, broker or dealer quotations or other observable inputs. Restricted cash consists primarily of funds held to satisfy the requirements of certain agreements that are restricted in their use and is included in non-current assets on the Company's consolidated balance sheet.
Concentration of Credit Risk	Concentration of Credit Risk The Company's financial instruments that are exposed to concentration of credit risk consist primarily of cash and cash equivalents and marketable securities. The Company maintains its cash and cash equivalents in bank accounts, which, at times, exceed federally insured limits. The Company invests its marketable securities in high-quality commercial financial instruments. The Company has not recognized any losses from credit risks on such accounts during any of the periods presented. The Company believes it is not exposed to significant credit risk on cash and cash equivalents or its marketable securities. The Company is subject to credit risk from its accounts receivable related to its product sales of Galafold ® . The Company's accounts receivable at March 31, 2019 have arisen from product sales primarily in the EU and U.S. The Company will periodically assess the financial strength of its customers to establish allowances for anticipated losses, if any. For accounts receivable that have arisen from named patient sales, the payment terms are predetermined and the Company evaluates the creditworthiness of each customer on a regular basis.
Revenue Recognition	Revenue Recognition The Company's net product sales consist of sales of Galafold ® for the treatment of Fabry disease. The Company has recorded revenue on sales where Galafold ® is available either on a commercial basis or through a reimbursed early access program ("EAP"). Orders for Galafold ® are generally received from distributors and pharmacies with the ultimate payor often a government authority. The Company recognizes revenue when its performance obligations to its customers have been satisfied, which occurs at a point in time when the pharmacies or distributors obtain control of Galafold ® . The transaction price is determined based on fixed consideration in the Company's customer contracts and is recorded net of estimates for variable consideration, which are third party discounts and rebates. The identified variable consideration is recorded as a reduction of revenue at the time revenues from sales of Galafold ® are recognized. The Company recognizes revenue to the extent that it is probable that a significant revenue reversal will not occur in a future period. These estimates may differ from actual consideration received. The Company evaluates these estimates each reporting period to reflect known changes.
Inventories and Cost of Goods Sold	Inventories and Cost of Goods Sold Inventories are stated at the lower of cost and net realizable value, determined by the first-in, first-out method. Inventories are reviewed periodically to identify slow-moving or obsolete inventory based on projected sales activity as well as product shelf-life. In evaluating the recoverability of inventories produced, the probability that revenue will be obtained from the future sale of the related inventory is considered and inventory value is written down for inventory quantities in excess of expected requirements. Expired inventory is disposed of and the related costs are recognized as cost of goods sold in the consolidated statements of operations. Cost of goods sold includes the cost of inventory sold, manufacturing and supply chain costs, product shipping and handling costs, provisions for excess and obsolete inventory, as well as royalties payable. A portion of the inventory available for sale was expensed as research and development costs prior to regulatory approval and as such the cost of goods sold and related gross margins are not necessarily indicative of future cost of goods sold and gross margin.
Leases	Leases In the ordinary course of business, the Company enters into lease agreements for office space as well as leases for certain property and equipment. The leases have varying terms and expirations and have provisions to extend or renew the lease agreement, among other terms and conditions, as negotiated. The Company determines if an arrangement is a lease at inception. Operating and finance leases are included in right-of-use ("ROU") assets and lease liabilities on the Company's consolidated balance sheets. ROU assets represent the Company's right to control the use of an explicitly or implicitly identified fixed asset for a period of time and lease liabilities represent the Company's obligation to make lease payments arising from the lease. Control of an underlying asset is conveyed to the Company if the Company obtains the rights to direct the use of and to obtain substantially all of the economic benefits from using the underlying asset. ROU assets and liabilities are recognized at commencement date based on the present value of lease payments over the lease term. Lease payments included in the measurement of the lease liability are comprised of fixed payments. Variable lease payments are excluded from the ROU assets and lease liabilities and are recognized in the period in which the obligation for those payments are incurred. Variable lease payments are presented in the Company's consolidated statements of operations in the same line item as expense arising from fixed lease payments for operating leases. The Company has lease agreements which include lease and non-lease components, which the Company accounts for as a single lease component for all underlying asset categories. A lessee is required to discount its unpaid lease payments using the interest rate implicit in the lease or, if that rate cannot be readily determined, its incremental borrowing rate. As most of the Company's leases do not provide an implicit rate, the Company uses its incremental borrowing rate based on the information available at commencement date in determining the present value of lease payments. The lease term for all the Company's leases includes the non-cancellable period of the lease plus any additional periods covered by either a Company option to extend (or not to terminate) the lease that the Company is reasonably certain to exercise, or an option to extend (or not to terminate) the lease controlled by the lessor. Leases with an initial term of 12 months or less are not recorded on the balance sheet. The Company recognizes lease expense for these leases on a straight-line basis over the lease term. The Company applies this policy to all underlying asset categories. The information presented for the periods prior to January 1, 2019 has not been restated and is reported under the accounting standard in effect for those periods.
Recent Accounting Developments	Recent Accounting Developments - Guidance Adopted in 2019 ASU 2016-02 - In February 2016, the FASB issued ASU 2016-02, Leases (Topic 842) ("ASU 2016-02"). ASU 2016-02 requires the recognition of lease assets and lease liabilities on the balance sheet for all lease obligations and disclosing key information about leasing arrangements. ASU 2016-02 requires the recognition of lease assets and lease liabilities by lessees for those leases classified as operating leases under previous generally accepted accounting principles. ASU 2016-02 will be effective for the Company for all annual and interim periods beginning after December 15, 2018, including interim periods within those fiscal years. In August 2018, the FASB issued ASU 2018-11, Leases (Topic 842): Targeted Improvements , ("ASU 2018-11"). ASU 2018-11 provide entities with an additional transition method for adoption, whereby, an entity initially applies the new leases standard at the adoption date and recognizes a cumulative-effect adjustment to the opening balance of retained earnings in the period of adoption. Effective January 1, 2019 the Company adopted ASU 2016-02, along with the amendments issued in 2017 and 2018, and elected the transition method in ASU 2018-11. The Company elected the package of transition provisions available for expired or existing contracts, which allowed the Company to carry forward its historical assessments of (i) whether contracts are or contain leases, (ii) lease classification and (iii) initial direct costs. In addition, the Company applied the short-term lease recognition exemption for leases with terms at inception not greater than 12 months and will apply the practical expedient not to separate lease and non-lease components for new and modified leases commencing after adoption. The information presented for the periods prior to January 1, 2019 has not been restated and is reported under the accounting standard in effect for those periods. Upon adoption, the Company recorded a lease liabilities with a corresponding right-of-use assets of $17.6 million . The adoption did not have a material impact on the consolidated results of operations and cash flows for the three-months ended March 31, 2019. In August 2018, the Securities Exchange Commission ("SEC") issued Final Rule 33-10532, Disclosure Update and Simplification , which amends certain disclosure requirements that were redundant, duplicative, overlapping or superseded by other SEC disclosure requirements. The amendments generally eliminated or otherwise reduced certain disclosure requirements of various SEC rules and regulations. However, in some cases, the amendments require additional information to be disclosed, including changes in stockholders' equity in interim periods. The rule is effective 30 days after its publication in the Federal Register. The rule was posted on October 4, 2018. On September 25, 2018, the SEC released guidance advising it will not object to a registrant adopting the requirement to include changes in stockholders' equity in the Form 10-Q for the first quarter beginning after the effective date of the rule. The Company adopted the guidance in this Form 10-Q for the period ended March 31, 2019. Recent Accounting Developments - Guidance Not Yet Adopted ASU 2018-13 — In August 2018, the FASB issued ASU 2018-03, Fair Value Measurement (Topic 820): Disclosure Framework-Changes to the Disclosure Requirements for Fair Value Measurement ("ASU 2018-13"). The amendments modify the disclosure requirements in Topic 820. ASU 2018-13 is effective for all entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2019. The amendments on changes in unrealized gains and losses, the range and weighted average of significant unobservable inputs used to develop Level 3 fair value measurements, and the narrative description of measurement uncertainty should be applied prospectively for only the most recent interim or annual period presented in the initial fiscal year of adoption. All other amendments should be applied retrospectively to all periods presented upon their effective date. Early adoption is permitted. An entity is permitted to early adopt any removed or modified disclosures upon issuance of ASU 2018-13 and delay adoption of the additional disclosures until their effective date. The Company is currently assessing the impact that this standard will have on its consolidated financial statements upon adoption. ASU 2017-08 — In March 2017, the FASB issued ASU 2017-08, Receivables—Nonrefundable Fees and Other Costs (Subtopic 310-20), Premium Amortization on Purchased Callable Debt Securities ("ASU 2017-08") . The amendments in ASU 2017-08 shorten the amortization period for certain callable debt securities held at a premium. Specifically, the amendments require the premium to be amortized to the earliest call date. The amendments do not require an accounting change for securities held at a discount; the discount continues to be amortized to maturity. ASU 2017-08 is effective for public business entities for fiscal years, and interim periods within those fiscal years, beginning after December 15, 2018. Early adoption is permitted, including adoption in an interim period. If an entity early adopts in an interim period, any adjustments should be reflected as of the beginning of the fiscal year that includes that interim period. The amendments should be applied on a modified retrospective basis, with a cumulative-effect adjustment directly to retained earnings as of the beginning of the period of adoption. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. ASU 2017-04 — In January 2017, the FASB issued ASU 2017-04, Intangibles - Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment ("ASU 2017-04"). To simplify the subsequent measurement of goodwill, ASU 2017-04 eliminates Step 2 from the goodwill impairment test. The annual, or interim, goodwill impairment test is performed by comparing the fair value of a reporting unit with its carrying amount. An impairment charge should be recognized for the amount by which the carrying amount exceeds the reporting unit's fair value; however, the loss recognized should not exceed the total amount of goodwill allocated to that reporting unit. In addition, income tax effects from any tax deductible goodwill on the carrying amount of the reporting unit should be considered when measuring the goodwill impairment loss, if applicable. ASU 2017-04 also eliminates the requirements for any reporting unit with a zero or negative carrying amount to perform a qualitative assessment and, if it fails that qualitative test, to perform Step 2 of the goodwill impairment test. An entity still has the option to perform the qualitative assessment for a reporting unit to determine if the quantitative impairment test is necessary. ASU 2017-04 should be applied on a prospective basis. The nature of and reason for the change in accounting principle should be disclosed upon transition. A public business entity that is a U.S. SEC filer should adopt ASU 2017-04 for its annual or any interim goodwill impairment tests in fiscal years beginning after December 15, 2019. Early adoption is permitted for interim or annual goodwill impairment tests performed on testing dates after January 1, 2017. The Company is currently assessing the impact that this standard will have on its consolidated financial statements. ASU 2016-13 — I n June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"). ASU 2016-13 requires financial assets measured at amortized cost basis to be presented at the net amount expected to be collected and amends guidance on the impairment of financial instruments. ASU 2016-13 is effective for public companies who are SEC filers for fiscal years beginning after December 15, 2019, including interim periods within those years. The Company expects to adopt this guidance when effective and is currently assessing the impact that this standard will have on its consolidated financial statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies Summary of Significant Accounting Policies (Tables)	3 Months Ended
	Mar. 31, 2019
Accounting Policies [Abstract]
Disaggregation of Revenue	The following table summarizes the Company's net product sales from Galafold ® disaggregated by geographic area: Three Months Ended March 31, (in thousands) 2019 2018 U.S. $ 9,068 $ — Ex-U.S. 24,978 16,696 Total net product sales $ 34,046 $ 16,696

Cash, Cash Equivalents, Marke_2

Cash, Cash Equivalents, Marketable Securities and Restricted Cash (Tables)	3 Months Ended
	Mar. 31, 2019
Cash, Cash Equivalents, and Short-term Investments [Abstract]
Schedule of cash and available-for-sale securities	Cash, cash equivalents and marketable securities are classified as current unless mentioned otherwise below and consisted of the following: As of March 31, 2019 (in thousands) Cost Gross unrealized Gain Gross unrealized Loss Fair Value Cash and cash equivalents $ 96,349 $ — $ — $ 96,349 Corporate debt securities, current portion 138,194 96 (6 ) 138,284 Commercial paper 134,948 52 (7 ) 134,993 Asset-backed securities 68,278 30 (8 ) 68,300 Money market 350 — — 350 Certificates of deposit 51 — — 51 $ 438,170 $ 178 $ (21 ) $ 438,327 Included in cash and cash equivalents $ 96,349 $ — $ — $ 96,349 Included in marketable securities, current and non-current 341,821 178 (21 ) 341,978 Total cash, cash equivalents and marketable securities $ 438,170 $ 178 $ (21 ) $ 438,327 As of December 31, 2018 (in thousands) Cost Gross unrealized Gain Gross unrealized Loss Fair Value Cash and cash equivalents $ 79,749 $ — $ — $ 79,749 Corporate debt securities, current portion 240,969 7 (250 ) 240,726 Commercial paper 115,245 — (104 ) 115,141 Asset-backed securities 68,215 4 (84 ) 68,135 Money market 350 — — 350 Certificates of deposit 51 — — 51 $ 504,579 $ 11 $ (438 ) $ 504,152 Included in cash and cash equivalents $ 79,749 $ — $ — $ 79,749 Included in marketable securities 424,830 11 (438 ) 424,403 Total cash, cash equivalents and marketable securities $ 504,579 $ 11 $ (438 ) $ 504,152
Schedule of restricted cash and cash equivalents	The following table provides a reconciliation of cash and cash equivalents and restricted cash reported within the consolidated balance sheets that sum to the total of the same such amounts shown in the Company's consolidated statements of cash flows. (in thousands) March 31, 2019 December 31, 2018 March 31, 2018 December 31, 2017 Cash and cash equivalents $ 96,349 $ 79,749 $ 114,322 $ 49,060 Restricted cash 2,579 2,626 2,230 2,177 Cash and cash equivalents and restricted cash shown in the statement of cash flows $ 98,928 $ 82,375 $ 116,552 $ 51,237

Inventories (Tables)

Inventories (Tables)	3 Months Ended
	Mar. 31, 2019
Inventory Disclosure [Abstract]
Schedule of inventories for the period	The following table summarizes the components of inventories: (in thousands) March 31, 2019 December 31, 2018 Raw materials $ 1,321 $ 1,291 Work-in-process $ 3,041 3,485 Finished goods 3,805 3,614 Total inventories $ 8,167 $ 8,390

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2019
Debt Disclosure [Abstract]
Schedule of liability components of the Convertible Notes	The Convertible Notes and Senior Secured Term Loan consist of the following: Liability component (in thousands) March 31, 2019 December 31, 2018 Principal 180,702 $ 400,000 Less: debt discount (1) (11,076 ) (74,145 ) Less: deferred financing (1) (808 ) (4,115 ) Net carrying value of the debt $ 168,818 $ 321,740 ______________________________________ (1) Included in the consolidated balance sheets within Convertible Notes and Senior Secured Term Loan and amortized to interest expense over the remaining life of the Convertible Notes and Senior Secured Term Loan using the effective interest rate method.
Components of total interest expense recognized related to the Convertible Notes	The following table sets forth total interest expense recognized related to the Convertible Notes and Senior Secured Term Loan for the three months ended March 31, 2019 and 2018, respectively: Three Months Ended March 31, Interest component (in thousands) 2019 2018 Contractual interest expense 4,813 $ 1,887 Amortization of debt discount 1,559 2,472 Amortization of deferred financing 83 129 Total $ 6,455 $ 4,488

Share based Compensation (Table

Share based Compensation (Tables)	3 Months Ended
	Mar. 31, 2019
Disclosure of Compensation Related Costs, Share-based Payments [Abstract]
Schedule of Fair Value of Options	The fair value of the stock options granted is estimated on the date of grant using a Black-Scholes option pricing model with the following weighted-average assumptions: Three Months Ended March 31, 2019 2018 Expected stock price volatility 74.2 % 81.2 % Risk free interest rate 2.5 % 2.3 % Expected life of options (years) 5.68 5.67 Expected annual dividend per share $ — $ —
Schedule of Stock Options Activity	A summary of the Company's stock options for the three months ended March 31, 2019 were as follows: Number of Shares Weighted Average Exercise Price Weighted Average Remaining Contractual Life Aggregate Intrinsic Value (in thousands) (in millions) Options outstanding, December 31, 2018 15,810 $ 8.63 Granted 3,315 $ 10.15 Exercised (578 ) $ 6.83 Forfeited (195 ) $ 10.33 Expired (21 ) $ 10.77 Options outstanding, March 31, 2019 18,331 $ 8.94 6.9 years $ 90.2 Vested and unvested expected to vest, March 31, 2019 17,325 $ 8.84 6.8 years $ 87.1 Exercisable at March 31, 2019 10,538 $ 7.84 5.5 years $ 62.8
Schedule of Non-Vested RSU Activity under the Plan	A summary of non-vested RSU activity under the Plan for the three months ended March 31, 2019 is as follows: Number of Shares Weighted Average Grant Date Fair Value Weighted Average Remaining Years Aggregate Intrinsic Value (in thousands) (in millions) Non-vested units as of December 31, 2018 3,712 $ 10.59 Granted 3,031 $ 10.91 Vested (600 ) $ 9.07 Forfeited (133 ) $ 12.73 Non-vested units as of March 31, 2019 6,010 $ 10.86 3.0 years $ 81.7
Schedule of Equity Compensation Expenses	The following table summarizes information related to compensation expense recognized in the statements of operations related to the equity awards: Three Months Ended March 31, (in thousands) 2019 2018 Equity compensation expense recognized in: Research and development expense $ 5,032 $ 3,057 Selling, general and administrative expense 7,712 4,421 Total equity compensation expense $ 12,744 $ 7,478

Assets and Liabilities Measur_2

Assets and Liabilities Measured at Fair Value (Tables)	3 Months Ended
	Mar. 31, 2019
Fair Value Disclosures [Abstract]
Summary of assets and liabilities subject to fair value measurements	A summary of the fair value of the Company's recurring assets and liabilities aggregated by the level in the fair value hierarchy within which those measurements fall as of March 31, 2019 are identified in the following table: (in thousands) Level 2 Total Assets: Commercial paper $ 134,993 $ 134,993 Asset-backed securities 68,300 68,300 Corporate debt securities 138,284 138,284 Money market funds 3,963 3,963 $ 345,540 $ 345,540 Level 2 Level 3 Total Liabilities: Contingent consideration payable $ — $ 20,767 $ 20,767 Deferred compensation plan liability 3,613 — 3,613 $ 3,613 $ 20,767 $ 24,380 A summary of the fair value of the Company's recurring assets and liabilities aggregated by the level in the fair value hierarchy within which those measurements fall as of December 31, 2018 are identified in the following table: (in thousands) Level 2 Total Assets: Commercial paper $ 115,141 $ 115,141 Asset-backed securities 68,135 68,135 Corporate debt securities 240,726 240,726 Money market funds 3,082 3,082 $ 427,084 $ 427,084 Level 2 Level 3 Total Liabilities: Contingent consideration payable $ — $ 19,700 $ 19,700 Deferred compensation plan liability 2,732 — 2,732 $ 2,732 $ 19,700 $ 22,432
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Schedule of changes in contingent consideration payable	The following table shows the change in the balance of contingent consideration payable for the three months ended March 31, 2019 and 2018 , respectively: Three Months Ended March 31, (in thousands) 2019 2018 Balance, beginning of the period $ 28,700 $ 25,400 Payment of contingent consideration in stock (9,316 ) — Changes in fair value during the period, included in Statement of Operations 1,383 1,100 Balance, end of the period $ 20,767 $ 26,500
Callidus Biopharma Inc
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Schedule of significant unobservable inputs used in the valuation of the contingent consideration payable	The following significant unobservable inputs were used in the valuation of the contingent consideration payable of Callidus for the ATB200 Pompe program: Contingent Consideration Liability Fair Value as of Valuation Technique Unobservable Input Range (in thousands) Discount rate 10.3% Clinical and regulatory milestones $ 20,538 Probability weighted discounted cash flow Probability of achievement of milestones 75%-78% Projected year of payments 2021-2022

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2019
Leases [Abstract]
Lease costs	Supplemental balance sheet information related to operating leases was as follows. (in thousands, except year and discount rate amounts) March 31, 2019 Operating lease ROU asset $ 36,208 Current portion of the operating lease liabilities $ 2,421 Non-current portion of the operating lease liabilities 35,991 Total operating lease liability $ 38,412 Weighted-average remaining lease terms (years) 14.6 Weighted-average discount rate 12.8 %
Future minimum lease payments, operating leases	At March 31, 2019 , the future minimum lease payments were as follows: ( in thousands) Operating Leases 2019 (excludes the three months ended March 31, 2019) $ 4,494 2020 9,776 2021 10,516 2022 10,418 2023 10,830 Thereafter 174,006 Total lease payments $ 220,040 Less lease incentives (28,939 ) Less imputed interest (152,689 ) Total operating lease liability $ 38,412
Schedule of future minimum lease payments	At December 31, 2018 , the future minimum lease payments were as follows: ( in thousands) Operating Leases 2019 $ 6,244 2020 4,063 2021 3,560 2022 3,371 2023 3,611 Thereafter 10,038 Total lease payments $ 30,887

Basic and Diluted Net Loss pe_2

Basic and Diluted Net Loss per Common Share (Tables)	3 Months Ended
	Mar. 31, 2019
Earnings Per Share [Abstract]
Schedule of reconciliation of the numerator and denominator used in computing basic and diluted net loss per common share	The following table provides a reconciliation of the numerator and denominator used in computing basic and diluted net loss attributable to common stockholders per common share: Three Months Ended March 31, (in thousands, except per share amounts) 2019 2018 Numerator: Net loss attributable to common stockholders $ (120,299 ) $ (49,916 ) Denominator: Weighted average common shares outstanding — basic and diluted 213,519,287 175,977,700
Schedule of potential shares of common stock that were excluded from the computation as they were anti-dilutive using the treasury stock method	The table below presents potential shares of common stock that were excluded from the computation as they were anti-dilutive using the treasury stock method: As of March 31, (in thousands) 2019 2018 Options to purchase common stock 18,331 16,176 Convertible notes 5,017 40,850 Outstanding warrants, convertible to common stock 2,554 3,110 Unvested restricted stock units 6,010 3,541 Vested restricted stock units, unissued 189 90 Total number of potentially issuable shares 32,101 63,767

Business (Details)

Business (Details) $ / shares in Units, $ in Thousands, shares in Millions	Mar. 31, 2019USD ($)program$ / sharesshares	Dec. 31, 2018USD ($)$ / shares
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of gene therapy programs | program	14
Exchange agreement, aggregate principal amount	$ 219,300
Shares authorized for issuance (in shares) | shares	39
Common stock, par value (in dollars per share) | $ / shares	$ 0.01	$ 0.01
Accumulated deficit	$ (1,532,521)	$ (1,412,222)

Summary of Significant Accoun_4

Summary of Significant Accounting Policies (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Jan. 01, 2019
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Allowance for doubtful accounts receivable	$ 300
Net product sales	34,046	$ 16,696
Operating lease, liability	38,412
Operating lease ROU asset	36,208
ASU 2016-02
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Operating lease, liability			$ 17,600
Operating lease ROU asset	15,000
U.S.
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net product sales	9,068	0
Ex-U.S.
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
Net product sales	$ 24,978	$ 16,696

Cash, Cash Equivalents, Marke_3

Cash, Cash Equivalents, Marketable Securities and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Cash, Money Market Funds, and Marketable Securities
Cash and cash equivalents	$ 96,349	$ 79,749	$ 114,322	$ 49,060
Fair value, Available-for-sale debt securities	341,978	424,403
Fair Value, Cash balances	96,349	79,749
Cost, available-for-sale securities	341,821	424,830
Gross unrealized gain, available-for-sale securities	178	11
Gross unrealized loss, available-for-sale securities	(21)	(438)
Cost, Cash balances and available-for-sale securities	438,170	504,579
Gross unrealized gain, Cash balances and available-for-sale securities	178	11
Gross unrealized loss, Cash balances and available-for-sale securities	(21)	(438)
Fair value, Cash balances and available-for-sale securities	438,327	504,152
Corporate debt securities, current portion
Cash, Money Market Funds, and Marketable Securities
Fair value, Available-for-sale debt securities	138,284	240,726
Cost, available-for-sale securities	138,194	240,969
Gross unrealized gain, available-for-sale securities	96	7
Gross unrealized loss, available-for-sale securities	(6)	(250)
Commercial paper
Cash, Money Market Funds, and Marketable Securities
Fair value, Available-for-sale debt securities	134,993	115,141
Cost, available-for-sale securities	134,948	115,245
Gross unrealized gain, available-for-sale securities	52	0
Gross unrealized loss, available-for-sale securities	(7)	(104)
Asset-backed securities
Cash, Money Market Funds, and Marketable Securities
Fair value, Available-for-sale debt securities	68,300	68,135
Cost, available-for-sale securities	68,278	68,215
Gross unrealized gain, available-for-sale securities	30	4
Gross unrealized loss, available-for-sale securities	(8)	(84)
Money market
Cash, Money Market Funds, and Marketable Securities
Fair value, Available-for-sale debt securities	350	350
Cost, available-for-sale securities	350	350
Gross unrealized gain, available-for-sale securities	0	0
Gross unrealized loss, available-for-sale securities	0	0
Certificates of deposit
Cash, Money Market Funds, and Marketable Securities
Fair value, Available-for-sale debt securities	51	51
Cost, available-for-sale securities	51	51
Gross unrealized gain, available-for-sale securities	0	0
Gross unrealized loss, available-for-sale securities	$ 0	$ 0

Cash, Cash Equivalents, Marke_4

Cash, Cash Equivalents, Marketable Securities and Restricted Cash - Additional Information (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2019	Dec. 31, 2018	Mar. 31, 2018	Dec. 31, 2017
Cash, Cash Equivalents, and Short-term Investments [Abstract]
Realized gain (loss) on debt securities	$ 0	$ 0
Fair value of available-for-sale debt securities in unrealized loss positions	100,400,000	403,100,000
Cash and cash equivalents	96,349,000	79,749,000	$ 114,322,000	$ 49,060,000
Restricted cash	2,579,000	2,626,000	2,230,000	2,177,000
Cash and cash equivalents and restricted cash shown in the statement of cash flows	$ 98,928,000	$ 82,375,000	$ 116,552,000	$ 51,237,000

Inventories (Details)

Inventories (Details) - USD ($) $ in Thousands	Mar. 31, 2019	Dec. 31, 2018
Inventory Disclosure [Abstract]
Raw materials	$ 1,321	$ 1,291
Work-in-process	3,041	3,485
Finished goods	3,805	3,614
Total inventories	$ 8,167	8,390
Reserve for inventory		$ 200

Debt - Convertible Debt (Detail

Debt - Convertible Debt (Details)	Feb. 16, 2018shares	Feb. 15, 2018USD ($)shares	Sep. 30, 2018USD ($)	Dec. 31, 2016USD ($)day$ / sharesshares	Mar. 31, 2019USD ($)$ / sharesshares	Mar. 31, 2018USD ($)	Dec. 31, 2018USD ($)$ / shares
Convertible Debt
Derivative liability, noncurrent		$ 507,400,000
Change in fair value of derivatives					$ 0	$ 4,861,000
Derivative liabilities					80,600,000
Capped call confirmation, current					2,200,000
Exchange agreement, aggregate principal amount					$ 219,300,000
Shares authorized for issuance (in shares) | shares					39,000,000
Common stock, par value (in dollars per share) | $ / shares					$ 0.01		$ 0.01
Exchange agreement, accrued and unpaid interest					$ 1,000,000
Loss on exchange of convertible debt					36,123,000	0
Gain (loss) on extinguishment of debt, additional paid-in capital					(190,400,000)
Gain (loss) on extinguishment of debt, fair value of common shares issued					(400,000)
Proceeds from capped call confirmations, exchange of convertible debt					$ 14,632,000	0
Common Stock Capped Call Confirmation
Convertible Debt
Derivative asset, noncurrent		$ 13,600,000
Common Stock
Convertible Debt
Common stock issued from underwriting agreement (in shares) | shares	885,000	19,354,839
Over-allotment Option | Common Stock
Convertible Debt
Number of days granted underwriters for purchase of shares		30 days
Maximum number of additional shares granted to underwriters | shares	2,903,225
Convertible Notes
Convertible Debt
Threshold percentage					130.00%
Convertible Notes | Convertible Senior Notes 2016, Due 2023
Convertible Debt
Aggregate principal amount				$ 250,000,000
Net proceeds after deducting fees and estimated expenses				243,000,000
Proceeds for capped call confirmations				$ 13,500,000
Shares issued per increment of convertible debt | shares				40,849,675
Debt conversion ratio (in shares)				0.1633987
Conversion price (in dollars per share) | $ / shares				$ 6.12
Threshold consecutive trading days | day				30
Debt Instruments [Abstract]
Principal					$ 180,702,000		$ 400,000,000
Less: debt discount					(11,076,000)		(74,145,000)
Less: deferred financing					(808,000)		(4,115,000)
Net carrying value of the debt					(168,818,000)		$ (321,740,000)
Interest expense
Contractual interest expense					4,813,000	1,887,000
Amortization of debt discount					1,559,000	2,472,000
Amortization of deferred financing					83,000	129,000
Total					$ 6,455,000	$ 4,488,000
Convertible Notes | Convertible Senior Notes 2016, Due 2023 | Minimum
Convertible Debt
Threshold trading days				20 days
Convertible Notes | Convertible Senior Notes 2016, Due 2023 | Over-allotment Option | Private Placement Purchase Agreement
Convertible Debt
Aggregate principal amount				$ 25,000,000
Line of Credit
Debt Instruments
New credit facility borrowing capacity			$ 150,000,000
Debt instrument term			5 years
Periodic payment, percentage			12.50%
Proceeds from issuance of debt			$ 146,600,000
Line of Credit | LIBOR
Debt Instruments
Basis spread on variable rate			7.50%

Stockholders' Equity - Common S

Stockholders' Equity - Common Stock and Warrants (Details) - USD ($) $ / shares in Units, $ in Thousands	Feb. 16, 2018	Feb. 15, 2018	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018
Collaborative Agreements
Proceeds of exercise of warrants			$ 812	$ 0
Exchange agreement, aggregate principal amount			$ 219,300
Shares authorized for issuance (in shares)			39,000,000
Common stock, par value (in dollars per share)			$ 0.01		$ 0.01
Contingent consideration, milestone payment			$ 9,000
Milestone payment, stock issued as consideration			$ 9,000
Common Stock
Collaborative Agreements
Common stock issued from underwriting agreement (in shares)			301,058	181,868
Milestone payment, stock issued as consideration			$ (9,300)
Common Stock
Collaborative Agreements
Common stock issued from underwriting agreement (in shares)	885,000	19,354,839
Outstanding warrants, convertible to common stock
Collaborative Agreements
Common stock issued from underwriting agreement (in shares)			101,787
Proceeds of exercise of warrants			$ 800
Outstanding warrants, convertible to common stock | Common Stock
Collaborative Agreements
Warrants exercise price (in dollars per share)			$ 7.98

Share based Compensation - Weig

Share based Compensation - Weighted-average Assumptions (Details) - Options to purchase common stock - $ / shares	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Expected stock price volatility	74.20%	81.20%
Risk free interest rate	2.50%	2.30%
Expected life of options (years)	5 years 248 days	5 years 244 days
Expected annual dividend per share (in dollars per share)	$ 0	$ 0

Share based Compensation - Stoc

Share based Compensation - Stock Option Activity (Details) - Options to purchase common stock $ / shares in Units, shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Options outstanding, December 31, 2018 (in shares) | shares	15,810
Options, Granted (in shares) | shares	3,315
Options, Exercised (in shares) | shares	(578)
Options, Forfeited (in shares) | shares	(195)
Options, Expired (in shares) | shares	(21)
Options outstanding, March 31, 2019 (in shares) | shares	18,331
Options, Vested and unvested expected to vest, March 31, 2019 (in shares) | shares	17,325
Options, Exercisable at March 31, 2019 (in shares) | shares	10,538
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Option outstanding, December 31, 2018 (in dollars per share) | $ / shares	$ 8.63
Options, Granted (in dollars per share) | $ / shares	10.15
Options, Exercised (in dollars per share) | $ / shares	6.83
Options, Forfeited (in dollars per share) | $ / shares	10.33
Options, Expired (in dollars per share) | $ / shares	10.77
Option outstanding, March 31, 2019 (in dollars per share) | $ / shares	8.94
Options, Vested and unvested expected to vest, March 31, 2019 (in dollars per share) | $ / shares	8.84
Options, Exercisable at March 31, 2019 (in dollars per share) | $ / shares	$ 7.84
Share-based Compensation Arrangement by Share-based Payment Award, Options, Additional Disclosures [Abstract]
Weighted average remaining contractual life, options outstanding, March 31, 2019	6 years 11 months
Weighted average remaining contractual life, options vested and unvested expected to vest, March 31, 2019	6 years 9 months
Weighted average remaining contractual life, options exercisable at March 31, 2019	5 years 6 months
Aggregate intrinsic value, options outstanding, March 31, 2019 | $	$ 90.2
Aggregate intrinsic value, vested and unvested expected to vest, March 31, 2019 | $	87.1
Aggregate intrinsic value, exercisable at March 31, 2019 | $	$ 62.8

Share based Compensation - Narr

Share based Compensation - Narrative (Details) $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)shares
Options to purchase common stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation costs | $	$ 44.1
Unrecognized compensation costs, period for recognition (in years)	3 years
Unvested restricted stock units
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
RSUs vested and non-vested units expected to vest (in shares) | shares	599,734
Unvested restricted stock units | Stock Option Plan Amended Restated 2007 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total unrecognized compensation costs | $	$ 48.2
Unrecognized compensation costs, period for recognition (in years)	3 years
RSUs vested and non-vested units expected to vest (in shares) | shares	600,000

Share based Compensation - RSUs

Share based Compensation - RSUs and PBRSUs Summary (Details) - Unvested restricted stock units $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2019USD ($)$ / sharesshares
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Vested (in shares)	(599,734)
Stock Option Plan Amended Restated 2007 Equity Incentive Plan
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Number of Shares [Roll Forward]
Non-vested units as of December 31, 2018 (in shares)	3,712,000
Granted (in shares)	3,031,000
Vested (in shares)	(600,000)
Forfeited (in shares)	(133,000)
Non-vested units as of March 31, 2019 (in shares)	6,010,000
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Nonvested, Weighted Average Grant Date Fair Value [Abstract]
Non-vested units as of December 31, 2018 (in dollars per share) | $ / shares	$ 10.59
Granted (in dollars per share) | $ / shares	10.91
Vested (in dollars per share) | $ / shares	9.07
Forfeited (in dollars per share) | $ / shares	12.73
Non-vested units as of March 31, 2019 (in dollars per share) | $ / shares	$ 10.86
Share-based Compensation Arrangement by Share-based Payment Award, Equity Instruments Other than Options, Additional Disclosures [Abstract]
Non-vested units, weighted average remaining years	3 years
Non-vested units, aggregate intrinsic value | $	$ 81.7

Share based Compensation - Expe

Share based Compensation - Expense Summary (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total equity compensation expense	$ 12,744	$ 7,478
Research and development expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total equity compensation expense	5,032	3,057
Selling, general and administrative expense
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Total equity compensation expense	$ 7,712	$ 4,421

Assets and Liabilities Measur_3

Assets and Liabilities Measured at Fair Value (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2019USD ($)	Dec. 31, 2018USD ($)
Assets:
Fair value of assets	$ 345,540	$ 427,084
Liabilities:
Contingent consideration payable	20,767	19,700
Deferred compensation plan liability	3,613	2,732
Fair value of liabilities	24,380	22,432
Exchange agreement, aggregate principal amount	219,300
Milestone payment, stock issued as consideration	9,000
Common Stock
Liabilities:
Milestone payment, stock issued as consideration	(9,300)
T B200 Pompe Program | Contingent Consideration Liability Clinical and Regulatory Milestones | Callidus Biopharma Inc
Liabilities:
Contingent consideration payable	$ 20,538
T B200 Pompe Program | Contingent Consideration Liability Clinical and Regulatory Milestones | Probability of Milestone Achievement | Minimum | Callidus Biopharma Inc
Liabilities:
Discount rate	0.750
T B200 Pompe Program | Contingent Consideration Liability Clinical and Regulatory Milestones | Probability of Milestone Achievement | Maximum | Callidus Biopharma Inc
Liabilities:
Discount rate	0.780
Commercial paper
Assets:
Fair value of assets	$ 134,993	115,141
Asset-backed securities
Assets:
Fair value of assets	68,300	68,135
Corporate debt securities
Assets:
Fair value of assets	138,284	240,726
Money market funds
Assets:
Fair value of assets	3,963	3,082
Level 2
Assets:
Fair value of assets	345,540	427,084
Liabilities:
Contingent consideration payable	0	0
Deferred compensation plan liability	3,613	2,732
Fair value of liabilities	3,613	2,732
Convertible debt, fair value	71,600
Level 2 | Commercial paper
Assets:
Fair value of assets	134,993	115,141
Level 2 | Asset-backed securities
Assets:
Fair value of assets	68,300	68,135
Level 2 | Corporate debt securities
Assets:
Fair value of assets	138,284	240,726
Level 2 | Money market funds
Assets:
Fair value of assets	3,963	3,082
Level 3
Liabilities:
Contingent consideration payable	20,767	19,700
Deferred compensation plan liability	0	0
Fair value of liabilities	$ 20,767	$ 19,700
Level 3 | T B200 Pompe Program | Contingent Consideration Liability Clinical and Regulatory Milestones | Probability Weighted Discounted Cash Flow | Discount Rate | Callidus Biopharma Inc
Liabilities:
Discount rate	0.103

Assets and Liabilities Measur_4

Assets and Liabilities Measured at Fair Value - Level 3 Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Balance, beginning of the period	$ 28,700	$ 25,400
Payment of contingent consideration in stock	(9,316)	0
Changes in fair value during the period, included in Statement of Operations	1,383	1,100
Balance, end of the period	$ 20,767	$ 26,500

Leases (Details)

Leases (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Dec. 31, 2018
Leases [Abstract]
Lease, renewal term	25 years
Operating lease cost	$ 2,100
Finance lease cost	100
Cash paid for amounts included in operating lease liabilities	1,400
Right-of-use assets obtained in exchange for new operating lease liabilities	19,500
Operating lease ROU asset	36,208
Current portion of the operating lease liabilities	2,421
Non-current portion of the operating lease liabilities	35,991
Total operating lease liability	$ 38,412
Weighted-average remaining lease terms (years)	14 years 219 days
Weighted-average discount rate	12.80%
Operating Leases
2019 (excludes the three-months ended March 31, 2019)	$ 4,494
2020	9,776
2021	10,516
2022	10,418
2023	10,830
Thereafter	174,006
Total	220,040
Less lease incentives	(28,939)
Less imputed interest	$ (152,689)
Operating Leases, Future Minimum Payments Due, Fiscal Year Maturity [Abstract]
2019		$ 6,244
2020		4,063
2021		3,560
2022		3,371
2023		3,611
Thereafter		10,038
Total lease payments		$ 30,887

Basic and Diluted Net Loss pe_3

Basic and Diluted Net Loss per Common Share (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Numerator:
Net loss attributable to common stockholders	$ (120,299)	$ (49,916)
Denominator:
Weighted-average common shares outstanding - basic and diluted (in shares)	213,519,287	175,977,700
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	32,101,000	63,767,000
Options to purchase common stock
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	18,331,000	16,176,000
Convertible notes
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	5,017,000	40,850,000
Outstanding warrants, convertible to common stock
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	2,554,000	3,110,000
Unvested restricted stock units
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	6,010,000	3,541,000
Vested restricted stock units, unissued
Denominator:
Antidilutive securities excluded from computation of diluted earnings per share (in shares)	189,000	90,000

Uncategorized Items - fold-2019

Label	Element	Value
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ 0
Retained Earnings [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	383,000
Comprehensive Income [Member]
Cumulative Effect of New Accounting Principle in Period of Adoption	us-gaap_CumulativeEffectOfNewAccountingPrincipleInPeriodOfAdoption	$ (383,000)